Course guidance system



June 1960 M. A. KARPELES I ,943,321

COURSE GUIDANCE SYSTEM Filed Jan. 6, 1958 5 Sheets-Sheet 1 la/k/l I l 17404 A azAco/v M5906 DES/R60 (DI/RS6 Full/Rf POS/770/V In venlor MARK A.KARPELfS I I lN/T/AL POSITION Attorney Filed Jan. 6, 1958 June 28, 1960KARPELES 2,943,321

COURSE GUIDANCE SYSTEM 5 Sheets-Sheet 2 SEA LEVEL MAGNET/C NOR Tb A A A,0 I nvenlor MARK A. KAIQPElES \o By A Home y June 28, 1960 M. A.KARPELES COURSE GUIDANCE SYSTEM 5 Sheets-Sheet 3 Filed Jan. 6, 1958 June28,1960 M. A. KARPELES 2,943,321

COURSE GUIDANCE SYSTEM Filed Jan. 6, 1958 5 Sheets-Sheet 4 a SYNC/I40 48AR/V-l 1 4 cam-mm: i Ln N M N fqo f 6 GEAR smvo 50x MomR L MARK A.KARPELES' Attorney June 28, 1960 Filed Jan. 6, 1958 M.A.KARPELES COURSEGUIDANCE SYSTEM 5 Sheets-Sheet 5 TRUE AIR I VOLTA G6 ADD/ 7' lO/v'BRIDGE OIFFEREWT/AL game ( 3 cos 8- 6) Aqc i GAS SWITCHES 5/70 65 ALSOSHOWN ABOVf' Inventor MARK A. KA'QPELES A Home y d si e ourse'a t'-m9s'.

t n mi in o i t infqrntauo it w h a rattrsurh a n aircraft; alo sa at bempl i d a r c n n cr byi mp yr fo m MM t e Pa ient A 21,943,321 COURSEnnrnANcnsys'rn A. Karpeles, West Orange, N.J., assignor to Intern ti nafie cnhon and l lcgranh til fhorafi n, Nu lley, N .J., a corporationofiMaryland time ran. '6, 195s, s no. 79 .3 a s sans .(cl; 361131-21 iThis invention relates tora'dio' ion y tms nd particularly to 'asystern' for A j j in in range O a o he 'h son, a m t ng he am ype inormat o and also as it moves betweenbe qiis inzones outside the n e othe bea n The Problem of p o id ngs e nsi if a ion to steer courses;-sttch as in .ILS ,orQother systems wh er a craft i di ted towa s a beaon, t nsp de 9r 'bndy'refle ting'e ectron asneti av s,- Othe p i r-nav taids employed to guide aircraft do not automatically provide i n nfrmation dir ctly to the p lot y which he can readily steer his craft to.follow any chosen course provided that course lies predominantly .wthinthe range of beacons transmitting position information.

hichdetect radio or Therefore, the principalfobject' of ,thisinventionis 'to P a a a on a d t sni e steerin of acraft s that it may follow anydesired course falling ptedominantly Withinthe range ofjbeaconstransmitting position information. 1' f Another object of this inventionis to provide a simple steeering signal to'the' pilotlof'a craft wherebyhe may readily control his craft to follow said desired course evenoutside the range of said beacons for a reasonable distance. Anotherobject of this invention is to provide a navigation system with which aknown land course may be maintained irrespective of the direction andvelocity or changes in the direction and velocity of the wind when thatcourse is within range of beacons transmittingpositionjinformation.Another object is to provide a navigation system with which a'known landcourse may be maintained even upon leaving the range of allof saidbeacons whereupon steering guidance is based upon dead reckoningprinciple and the wind velocity and direction when last established. l p

Another object is to provide an automatic steering guidance systemwhereby the pilot may set his. initial position and final desiredposition relativelto aknown position or may set his initial position anddesired course angle, then subsequently employ a simple null-typeindicator indicating deviations from the, desired course to guide thesteering of his craft.

A further object is to pi 'o'yide, automatic steering guidanceto guide acraft over a predetermined course falling in 2,943,321 Patented June 28,1960 '2 predomin ntly Within the range of oneor more beaconstransmitting polar coordinate position information, such as in the TACANradio navigation system,;and employed in conjunction with the mobileepuipment of a said TACANsystem, such as the ARN-V21, to providesteering guidance'to the pilot of said craft and to further provide awind computer which automaticallycomputes the wind vector and may beoperated so :as to produce as inputs to an A.-C.- analog steeringcomputer from which to energize a null-type indicator indicatingdeviations oneithe'r side of said desired course whetherth'at course bedirectly towards said TACAN beacons or a skew course. v

It is another feature .of this invention to employ-an A.C. analogrtypewind computer responsive to-said polar GQordinate information fromtheARN-Zlreceiver, air.- craft heading and true air speed to compute windvelocity and di'rection'sothat upon-leaving therange of all ofsaidfheacons or uponthe failure of said ARNTZI receiver to receivesaidppolar coordinate information, said analog';type wind computer maybe employed in reverse to -computeethe missing polarcoordinate-information'which is indicative of the crafts position as afunction ,ofthelast computed wind velocity and direction, craft heading,and .true air speed, yielding the missing polarcoordinate--information"input to said A.C. analog steering computer andcausing it tocontinue to .provide steering information via saidnull-type indicator after said failureor after the craft leaves the.rangeof all of said beacons. c

Other and further features and objects of this inventionwill be moreapparent from the following specific description. taken in conjunctionwith the figures in which: a Y a .Fig. 1 depicts a typial straight lineskew course passing within .the ranges andbetween the ranges of typicalTACAN beacons and extending from an initialpoint of departure to a.destination or final point; a

Fig. 2 depicts .the relationship between aircraft position .and TACANbeacon position and the direct and horizontal distances between them; a

Fig. 3 depicts the angles and distances and polar coordinatesfrom whichto better understand the function of the skew-course guidance computershown in Fig. 4;

Figs 4 depicts an electrical schematic and block diagram of the-skewcourse guidance computer;

Fig. 5 depicts angles and rates and polar coordinates from whichto:better understand the wind computer shown 'in Fig. 6; a a

Fig. 6A depicts one portion of an electrical schematic and block diagramof the reversible wind computer employe in conjunction with the skewcourse'guidance a sn es wn n. He 3; d

Fig. 6B depicts the remaining portion of the reversible windcomputer. VY7 Referring first to Fig. I, there is shown a planview of our positioninformation transmitting beacons A, B, C, V

and D. such as employed in the TACAN radio navigation system andreferred toas the URN-3;, Each of'these beacons transmits signals fromwhich two-dimensional ,vyhigh may be-kn wnor obtained from the samereceiver l r 3 V an angle p to the magnetic north vecto The initialcoordinates at the point of departure are p and 0 with respect to beaconA. The value p and 0 may be detected by the ARN-21 receiver of the TACANsystem or they may be known. Subsequently as the craft progresses alongline 1 towards point X, and 6, information from beacon A is received andtogether with p and 6 and is employed in the skew course computer shownin Fig. 4 to energize a null-type indicator indicating right or leftdeviations from the desired course line 1.

Upon reaching point X, the signal from beacon B is received producing anew set of initial coordinates p and 0,, which locate the craft withrespect to beacon B. These initial coordinates px and 0 may be manuallyset in the skew course computer shown in Fig. 4, or automatic means maybe provided so that as the craft continues along line 1 from X towardspoint W, the p and 0 information received by the ARN-21 receiver is thattransmitted from beaconB locating the craft relative to beacon B.

Meanwhile the wind computer shown in Fig. 6, which is responsive to 0,true air speed of the craft, .V and magnetic heading of the craft 7, hasbeen continually computing the wind vector by operating in what will bereferred to as the normal or N condition and will be subsequentlydescribed.- The wind vector iscomputed so that upon arriving at point Wwhere all beacon signals are lost, p and 0 signals (with respect tobeacon B) may be made available to the skew course computer. These p and0 signals are made available by operating the wind computer backward inwhat will bereferred to as the memory or. M condition, in response tothe last computed wind vector, true air speed, and magnetic heading.Thus, the skew course computer shown in Fig. 4, which derives p and 0signals from the TACAN ARN-21 receiver will continue to receive p and 0position information with respect to beacon B to yield steering guidanceto the pilot as the craft progresses from point X to point Y;

At point Y initial polar coordinate position information with respect tobeacon C is received, py and 0 which may be automatically fed to theskew course computer or manually set as shown in Fig. 4 so that flightmay continue along line 1 to point Z where the same action occurs again.Obviously, numerous beacons may be employed over an extended line offlight, and itis only required that the carrier frequency of subsequentbeacon signals be anticipated to insure a switch-over as described atpoints X and Z or to minimize the distance the craft will travel overwhich no beacon signal is received, such as from W to Y. t t

In order to achieve a higher level of accuracy so that the skew coursecomputer may provide guidance over a desired ground path, particularlywhen that path is close to a beacon and/ or the craft is at highaltitude, the projection of the distance p on the sea level plane,denoted r, is desired rather than the distance p itself. Means to solvethe right triangle formed by r, p, and the altitude difference betweenthe craft and the beacon are included in the skew course computer shownin Fig. 4 and will be described later. Fig. 2 is provided to aid inunderstanding the relationship between r and p. In this figure the craft2 a distance p from the beacon 3 and at an altitude H above sea level isa height H-H above the beacon. Obviously, the sum of A.C. voltagesproportional to H-H and r, if they are in quadrature, will be equal to avoltage proportional to p. Thus r may be equated electrically to p whenH and H, are known.

Referring next to Fig. 3, there is shown geometry to aid inunderstanding the operation of the skew course computer shown in Fig. 4.In Fig. 3, line 1 indicates the desired course or line of flight in adirection 45 with respect to magnetic north, said course commencing at 0which is described by ground polar coordinates r, and 0 and passingthrough any point P described by coordinates r and 0. Line L is aperpendicular from A to line 1 cross- 4 ing line 1 at point K.Obviously, line L is common to triangles OAK and PAK so that at anypoint P along line 1 the following relation exists:

Thus the difference between the left and the right members of thisequation is indicative of the craft deviation from the desired groundcourse represented by line 1.

Referring next to' Fig. 4, there is shown a skew course steeringcomputer employed in conjunction with the TACAN radio navigation system,which system is represented by a transmitter and responder beacon 3 (onetype being identified and known as the URN-3) located at some knownpoint on the ground and the ARN-Zl receiver and transmitter 4 in craft2. The outputs of ARN-21 receiver are a voltage proportional to p and ashaft rotation proportional to 0 which are indicative of the craftsposition with respect to,the location of the beacon 3. Shaft position!)is fed to normally engaged clutch 5 and thence to diiferential gear box6. The desired course 4: is set by manual course control 7 which feeds ashaft position proportional to to differential gear box 6 and todifferential gear box 8, which is also fed a shaft position proportionalto 49 from manual initial bearing control 9. Thus the shaft rotationoutput from differential gear box 6 is proportional to 0-4: and theoutput from differential gear box 8 is proportional to 0 These shaftpositions are fed to resolvers 10 and 11, respectively.

Resolver 10 receives a voltage proportional to r at its turn fedavoltage proportional to p from receiver 4 or,

when the final position of a desired course with respect to a givenbeacon, p; and 0; is known and 5 is not known, right triangle solver 13receives a voltage proportional to I): via line 14 from final positioninput control unit 15.

Resolver 11 receives a voltage proportional to r at its rotor coil Rfrom potentiometer 16 actuated by a shaft rotation proportional to frommanual initial distance control 17.

Thus the voltage output from resolver 10 at its stator coil S which isfed to line 18 is proportional to 1' sin (0) and the output fromresolver 11 at its stator coil 5;, which is fed to line 19 isproportional to r sin (9 when the value of r is derived from the outputof receiver 4 rather than unit 15. Lines 18 and 19 feed their signals tosumming circuit 20 where they are effectively compared sincepotentiometers 12 and 16 are energized by voltages of opposite polarity.Summing circuit 20 energizes error indicator 21 which is sensitive tophase and indicates deviations of the crafts position from desiredcourse line 1.

When the course angle p is not known but the coordinates of a positionon the course, as, for example, the final position 0;, are known as wellas the coordinates of some other position on the course, such as r 0then can be determined by the servo loop comprising motor 22 drivingnormally disengaged clutch 23 "in response to the output of servoamplifier 24 which is to coil 25. Manual control 26 positions switches27,

28, 29, and 30 at their respective F terminals and may be actuated bythe pilot when it istdesired to establish the setting 1: of manualcourse control 7. For this purpose manual p; control 31 driving pot 32and manual 0; control 33 feeding a shaft position to normally disengagedclutch 34 are provided so that when switches 27, 28, 29 and 30 arepositioned at their F terminals, coil 25 is energized causing clutch 23to engage, coils 35 and 36 are energized causing clutches 34 and 5 toengage and disengage, respectively, and p, rather than p t is fed toright triangle solver 13 via line 14. Consequently one shaft input todifferential gear box 6. is: 0 instead of 0 and a signal proportional tof is fed to resolverlOinstead of r and also the shaft position output ofmotor 21 is coupled to differential gear boxes6 and 8 and to manualcourse control 7'to establish: qs. Once qsis established in this mannercontrol 7 maybe locked and switches 27, 28,129; and 30 repositioned fornormal operation so that the skew coursecomputer providessteering"guidan'ce. t I

Right triangle solver} operates in thel'f ollowing manner to yield' ashaft pdsition' 'r output for a voltage.

p input (see also Fig. 2 A positive voltage 'derived from pressure.altitude transducer 37, and megative voltage derived from manual beaconaltitude (H Control 31$ (via potent 39) are a'p lied 1 20 1118 inputcircuit of servo 'amplifier40'where they are added to the voltage acrosscapacitor 41. The initial phasing between the voltage input and thesignalsjndicative of H and Hare such that the" voltage across capacitor41 is in phase with the voltages indicative of H at H fed to servoamplifier 40. The voltage impressed across capacitor 41 and. feedbackpot 42 is obtained from switches 29. and 30 and is proportional to .p'or if dc pending onthe-operation of unit 15. Feedbackpot'42' is variedby the shaft output of servo motor-.43 which is indicative of r. Thismotor is energized by th'elo'ut putof servo amplifier 39 Obviously, thevoltage int-l pressed across pct. 42 and capacitor 41, which are inseries, is proportional to la'nd can be represented two, vectorvoltages'in quadrature, for example, the volt age. across potentiometer42 which is equivalenti to r and the voltagea'cross capacitor 41 whichis equivalent to H-H Thujs motor 43 drives until the inputs to servoamplifier 40mm toze'r'o yieldinga shaft rotation indicative of r,

Turning now to Fig.5, there is shown a typicalcondition that is solvedbythe windcompute'r shown in Fig. 6. In Fig. 5 the aircraft 2 at point 0heading; at an angle 7 to magnetic north. at a true a'ir speedy andground speed V which form thedesired course angle 4: With magneticnorth. The position tllis described by p and 6 with respectto the,TAQAlI beacon at A1 The vector difference between V,, and Y is the windvector represented as V at an angle 0 to magnetic north. Other anglesand vectors are selfQe'irplahatory Briefly, the wind computer solvesthree right"triangles'successive1 1y to arrive at the magnitude anddirection of the wind vector (V and 0 Thesetr'ianglesl in' successionofsolution are identified by angles 5, and 0 v Referring now to Figs. 6A:and' 6B, there" is shown'the A.C. analog-type Wind computer: for solvingtheright triangles described above and comprising a 0 servo loop 44having a synchro 45 coupled to a synchro 46inthe ARN-21 TACAN receive'rto obtain a signal indicative of 0 which is differentiated bygenerator'47 producing avoltage proportional to dfl/dt in line 48. .Thesignal 7 from any TACAN beacon and the AGC voltage increasessufliciently, gas diode 67g will conduct and relay solenoid 67 will be.energized flipping each of switches 51 .t o 6 6 to their ,M or memoryopetation terminals at which time the wind computer. operates in reverseto computep and fi rather thanvwand e p Continuing in normalNfoperation; the p servo loop servo amplifier 76; servo motor 77, andjn'ormal ly engaged clutch 78. The ,3 shaft output'of clutchj78iis' alsocoupled to differential gear box 79. v, V

A shaft rotation, proportional t'o'the aircraft magnetic heading 7 isfed fromtransducer 80 to differential gear box 50, whose output shaftrotation is proportional to 0. y and is fed to difieiential gear box 79,and since differentialgear' box 79 is also fed a fishaft rotation, itsoutput shaft rotation represented by mechanical coupling line 81 isindicative of. .6. This 6 output from line 81 is coupled to resolver.82Qwhose rotor coil R1 is coupled to rotor'coil R of resolverj74. Thusstator coils S and'S of resolver 82 produce signalsindicative of V cos 8and V sin 6, respectively. TheHV cos 5 signal is fed via switch 61 tovoltage addition bridge 83 where true air speed voltage'fromtrue airspeed transducer 84 of the propersign is a'dded producing V cos 8 VWhich' is fedfto stator coil Si'ofresblYer SS via switch 62. Theothenstator coilof resolver 85 is fed V sin 5 from stator coils'ofresolver 82'; Thus, the voltage induced in rotor coitR dfresolver85' is indicative of V when the error voltage from coil R of thatresolver is nulled by the servo loop including amplifier 86, motor 87and'normally engaged clutch 88 which couples a shaft rotationproportioiial to' 9521' to resolver 85 and' to differential gear box 89.Gearbox 89 also re'ceives a shaft input from heading transducer 80 sothat its output shaft position is representative of 0 and may beindicated on 0 indicatch 90.

Rotor coil R of resolver 85 is coupled via switch 64 to a servo loopcomprising amplifier 91, switch 65, servo L ARN-Zl receiver for agiv' nperiod, such as occurs'when 68, responsive to a p voltage from TACANreceiver ARN-21 via line 69, produces a shaft rotation proporthe craftmoves from WtoY, shown in Fig. 1, and beacon signals are lost, relaysolenoid 67 is energized and switches 51 to 66 are positioned attheirterminals M, thus reversing the op'rationof thewind computer commencingmemory pe'rationin the M condition. Subsequently the shaftrotation from0 indicator 90 is fed back to differential gear box 89 and avoltageindicative of V is fed from Vw pot via switch 64 to rotor winding R ofresolver 85' and switch 66 applies D.C. energy to coils 96, 97, and 98disengaging, engaging, and disengaging clutches 88, 99, and 78,respectively. Thus resolvers 85, 82, and 74 operate in a manner that isthe reverse of the manner described during the normal or N operation.

7 Also true air speed transducer 84 applies a signal indicative of V viaswitch 63 to bridge; 83 whose output indicative of V cos 6 is fed viaswitch 62 of stator coil S of resolver 82. Also circuit 70 serves todivide pdQ/dt by p producing de/dt which is fed via line 75, switch 56and switch 52 to amplifier 100 in the 0 servo loop 44 and the output ofgenerator 47 of this loop is fed via switch 51 to amplifier I Thus servoloop '44 integrates the input dH/dt yielding a shaft rotation outputindicative of 0 which is fed via synchros 45 and 46 to the TACAN ARN-21receiver to replace the lost 0 signal and is also fed via line 49 todifferential gear box 50. Meanwhile the signal from stator coil S ofresolver 74, indicative of d /dt, is fed via switch 54 to amplifier 101of p servo loop 48 where it is integrated by the action of servo motor102, generator 72 and switches 54 and 53 to yield a shaft rotation at 71indicative of p. This shaft rotation is also fed to potentiometer 103via a gear box and the voltage output of potentiometer 103 which isindicative of p is then fed to TACAN receiver ARN-Zl to replace the lostp signal.

7 While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanying claims.

I claim: 7

1. A course guidance system comprising transmitting and receiving meansproducing a first set of signals indicative of the position. of a craftrelative to a known position means to generate a second set ofsignalsindicative of a selected position onsaid course relative to saidknown position, comparing means coupled to said.

transmitting and receiving means and to said means to generate signalsfor comparing said first set of signals with said second set of signals,indicating .means coupled to said comparing means to indicate deviationsof said craft from said course, directive means. for producing signalsindicative of said crafts velocity and heading, means coupled to saidtransmitting and receiving means and to said directive means to computewind velocity and direction, means coupled to said means to compute tostore signals indicative of said wind velocity and direction, said meansto compute being responsive in absence of said first set of signals tooperate in reverse to compute said first set of signals in response tosignals from said means to store thereby supplying said first set ofsignals to said comparing means;

2. In a radio navigational system having a beacon station whichtransmits positional information; a mobile receiver for receiving saidpositional information, a course computer coupled to said mobilereceiver employing said information to produce signals indicative ofdeviations of the position of said mobile receiver from a given course,directive means producing signals indicative of the velocity anddirection of travel. of said receiver, a wind computer coupled to saidmobile receiver and said directive means and responsive to saidpositional information and the velocity and direction of travel of saidreceiver to produce signals indicative of wind velocity and direction,storage means coupled to said wind computer to store said signalsindicative of wind velocity and direction and signal detection meanscoupling said Wind computer to said mobile receiver so that when saidreceiver fails to receive positional information said wind computer iscaused to be operated in reverse computing said positional informationin response to wind velocity and direction signals from said storagemeans and the velocity and direction of travel of said mobile receiverthereby supplying the positional information to said course computer.

3. A navigation aid providing steering information to guide a craft on agiven course comprising a plurality of beacons transmitting signals fromwhich the position of said craft may be obtained, and a mobile stationhaving means to receive and detect said transmitted signals means togenerate other signals indicative of second and third positions on saidgiven course, transducermeans producing signals indicative of saidcrafts velocity and heading, computing means responsive to said detectedsignals and said transducer means to compute thewind velocity anddirection, said computing means being coupled to said receiving means;by signal level detection means so that whensaid receiving means failsto receive said signals indicative of said crafts position, saidcomputing means is caused to be operated in a reverse manner producingsignals indicative of said crafts position which are coupled to saidreceiving means, means coupled to said means to produce signals and saidreceiving means for computing the angle of said course means to storesaid computed angle, means coupled to said receiving means, said meansto store and said means to generate signals for comparing said receivedsignals with said third set of signals when said angle isknown'producing a signal indicative of deviations of said craft fromsaid course, and indicating means coupled to said means for comparing toguide steering of said craft.

4. A navigation aid to guide steering of a craft over a given course andemployed in' conjunction with craft position detection means whichprovides coordinate signals indicative of the position of said craftcomprising means to produce other coordinate signals indicative of otherpositions on said given course, course angle computing means coupled tosaid means to produce signals, course angle storage means coupled tosaid course angle computing means, comparing means coupled to saiddetection means, said storage means and said means to produce forcomparing said coordinate signals indicative of craft position withcoordinatesignals indicative of one of said other positions as functionsot said course angle, producing a signal indicative of deviations ofsaid craft position from said course, craft heading and true air speedtransducers, wind computing means coupled to said detection means andsaid transducers to compute wind velocity and direction and meanscoupled to said wind computing means to store signals indicative of windvelocity and direction, said wind computing means being coupled to saiddetection means by means responsive to the level of said coordinatesignals indicative of craft position. so that when said level reaches apredetermined value said wind computer operates in reverse computingsaid signals indicative of craft position. v

5. A course guidance system to guide a craft over a given ground courseand employed in conjunction with radio distance and direction measuringequipment which yields signals indicative of the radio distance anddirection of said craft from a known point and including means toproduce other distance and direction signals indicative of groundpositions on said course, comprising means to convert radio distancesignals to an equivalent ground distance signal, means to store a signalindicative of the angle of said course, switching means responsive tomanual control for coupling radio distance signals from said measuringequipment and radio distance signals from said means to produce to saidmeans to convert, course angle computing means coupled to said means toproduce signals, said means to convert and said means to store,comparing means coupled to said means to produce signals, said means toconvert, said measuring equipment and said means to store for comparingone of said ground positions on said course with the position of saidcraft, indicating means coupled to said comparing means to indicatedeviations of said craft from said given course, craft true air speedand heading transducers, wind computing means coupled to said measuringequipment and said craft transducers and responsive to radio distanceand direction signals to compute wind velocity and direction and meanscoupled to said means to compute wind to store signals indicative ofsaid wind velocity and direction, said means to compute wind coupled tosaid measuring equipment by signal level detection means so that whensaid equipment fails to yield distance and direction signals of givenstrength, said means to compute Wind operates in reverse computing 9said signals indicative of 'adio distance and direction of said craftfrom said known point in response to signals from said meansto storeWind velocity and direction signals, thereby supplying said signalsindicative of radio distance and direction of said craft from said knownpoint.

References'Cited in the file of this patent UNITED STATES PATENTS ErgenJune 4, 1957

